How to replace the spark plug on a push lawn mower

When a lawn mower won't start, one of the most common culprits is a bad spark plug. Most lawn mower manufacturers recommend replacing the spark plug every year or so. If your lawn mower won't start, replacing the spark plug is a good first troubleshooting step because spark plugs are cheap (usually around $5 or $10) and easy to replace.

The exact instructions for replacing a spark plug will vary by mower model, but this guide walks you through the general procedure for replacing a spark plug in a push lawn mower. These instructions can be used on many different brands and models of lawn mowers.

Instructions

Step 1

Make sure the mower is off

If the lawn mower is running, shut it off now. Wait for the mower to completely die down before beginning to work on it.

Step 2

Disconnect the spark plug boot

The spark plug on most lawn mowers sits at the front of the mower, sticking out of the engine block. It draws the electricity required to create a spark through the wire that connects to it. This wire terminates in a large L-shaped connector, called the boot.

Disconnect the boot from the spark plug by pulling the boot away from the plug. It should snap off easily.

Step 3

Remove the spark plug

The spark plug can be screwed off using a pair of slip-joint pliers or a large adjustable wrench. (If you happen to have a spark plug wrench, that will also work.) Unscrew the plug by turning it counter-clockwise until it is free from its housing, then remove it.

Step 4

Install the new spark plug

Place the new spark plug into the cavity vacated by the old plug. Then screw it in place, turning it clockwise just until it sits snugly and won't unscrew by hand.

Step 5

Reattach the spark plug boot

Pop the spark plug boot back onto the spark plug. It should snap on so that it is securely attached to the plug.

Step 6

Test the mower

Start the mower up and see if the spark plug fires and the mower starts. If it doesn't, you may have a problem other than the spark plug, and you might want to have a professional take a look at the mower.

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Things Needed

Lawn mower

New spark plug (same kind as the old one)

Slip-joint pliers, large adjustable wrench, or spark plug wrench

Tips & Warnings

Always install a new spark plug of the same size and type as the spark plug being replaced.

Never attempt to work on a lawn mower while it is running.

	E3 Spark Plugs E3.10 Small Engine and Lawn & Garden Spark Plug , Pack of 1 Amazon Price: $3.99
	Briggs & Stratton 5095H L-Head Engine Spark Plug Amazon Price: $2.04
	Arnold 490-850-0001 3/4-Inch & 5/8-Inch Spark Plug Wrench Amazon Price: $5.19

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Greg Schwartz
Helium member since Jan 30, 08
Number of Guides: 213

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